A breathing mask of this kind is known from German Utility Model Application No. 67 52 895.
The known breathing mask has a molded body which can be placed over the area of the nose and mouth. The ambient air can be inhaled through a filter and is exhaled again through an exhalation valve. A bead of expandable plastic is provided for reliably sealing off the breathing mask at the surface of the skin in the nose and mouth area of the wearer. This peripheral bead is formed when the mask body is molded by appropriately increasing the cross section of the mold. Other regions of the mask body are provided with reinforcing elements such as metal sheets or plastic inlays which are inlaid into the appropriate molding tool during molding. The known breathing masks thus have a bead seated on and surrounding parts of the face of the wearer. The bead is made of soft plastic and the mask has a reinforced mask body for receiving a breathing filter or for mounting the exhalation valve.
In the known breathing masks, the soft configuration of various parts of the mask is attained only by a corresponding thickening of the cross section, so that there the expandable plastic can form a porous elastic core. A variable distribution of hardness in the mask body is therefore always associated with a variable wall thickness distributed over the mask. Freedom of design for the purpose of attaining a breathing mask that is comfortable to wear is considerably restricted thereby. Furthermore, the weight of the breathing mask is increased because of the inlaid reinforcing elements.
In other breathing masks, which are not made of expandable plastics, different wall thicknesses of relatively soft plastics are used. The masks are then made thin in the parts around the face. Locations that should be stronger are attained by means of larger wall thicknesses to very large wall thicknesses. These breathing masks have a high inherent weight because of the accumulation of larger wall thicknesses in the middle region of the mask.